Organisms that can convert one or more monosaccharides into one or more biochemicals such as biofuels are well known. For example, both genetically modified (referred to as GM) yeast and non-genetically modified (referred to as non-GM) yeast are well known organisms that can convert sugars into alcohols such as ethanol and butanol via fermentation.
Yeast can be conditioned under conditions similar to those used during fermentation so as to, e.g., help the yeast be more effective in producing one or more bioproducts such as ethanol. Oftentimes, conditioning is performed in a propagation system which is typically much smaller in volumetric size as compared to a fermentation system. The conditioned yeast can then be “pitched” (i.e., transferred) from a dedicated conditioning and/or propagating tank to a separate fermentation reactor (i.e., a fermentor). Propagation and conditioning tanks can be a source of bacterial contamination which can impact the performance of yeast during fermentation in a fermentation reactor to an undue degree (e.g., due to bacteria producing undue amounts of lactic acid).
An alternative to pitching yeast from a propagation tank and/or conditioning tank to a fermentation tank includes what is often referred to as “dry-batching.” Dry-batching involves directly pitching yeast into a single fermentation tank so as to eliminate propagation and/or conditioning tanks. For example, dry-batching can include directly pitching yeast into each batch fermentation tank of a fermentation system. Such dry-batching techniques can be very expensive due to the amount of fresh yeast pitched directly into each batch fermentation tank.
There is a continuing need to discover improved methods of pitching yeast into a fermentation system (e.g., multiple batch fermentation vessels) in a manner that avoids undue bacterial contamination and/or reduces the amount and cost of yeast.